These stations have the problem of adapting the pumping devices to the consumption, which s randomly distributed and which may vary over a wide range of values.
As has been said, the pumping devices start and stop such that the pressure in the fluid storage reservoir or reservoirs is maintained between two limit values of pressure: the start pressure which depends on certain minimum values that have to be maintained and the stop pressure, which depends on the number of start-ups per unit time.
The starting and stopping of the pumping devices is an ON/OFF operation and does not in any way take into account the possibility of adapting the station to the consumption.
Therefore, in order to guarantee the consumption requirements during peak hours, pumping stations tend to be oversized. This leads to frequent starting and stopping, since when the consumption is low the storage reservoirs are emptied very quickly in the case of vacuum, or fill very quickly in the case of positive pressures. The oversizing also means that the stations work for long periods of time consuming much more power than is strictly necessary for the consumption required. In no other way can one regard the high hysteresis set tip in order to guarantee a reduced number of start-ups.
This regulating system therefore involves a considerable waste of energy, as well as a high rate of wear of the pumping devices which reduces their life.
Furthermore, the start and stop conditions do not guarantee that the flow supplied by the set of pumping devices is suitably controlled. In fact it only controls the variable pressure directly.